Even with the advent of e-mail, facsimile (fax) remains an important and ubiquitous form of business communications. Virtually all businesses use fax; with some, it is critical to the business's mission. Some large multi-location enterprises send thousands of faxes every day between offices, spending tens-of-thousands of dollars every year on telephone toll charges.
The use of the Internet as an application platform for real-time media transport has disintermediated telecommunications. Users can transport voice calls across the Internet without the involvement of telephone companies. One of the earliest such services was that of Net2Phone®, which offered PC-to-PC communications for a fee paid to the company, not unlike a telephone company, but much less expensive.
Other services (e.g., Skype™) offer peer-to-peer (P2P) communication service over the Internet at no fee. The Skype™ P2P technology is characterized by a method of traversing firewalls and handling Network Address Translation (NAT) to allow Internet packets to flow in real time between the two correspondent Skype™ clients. Although there are other P2P networks, such as Napster™, File-Sharing, Collaboration, Freenet, and Gnutella, these networks are based on open-source software and are intended for data-file exchange, not real-time media data transfer, such as that required for a voice or a fax call.